PiXtend V2 -L- Hardware Manual
6.8. Real-Time-Clock
The real-time clock (RTC), the Raspberry Pi always provides the current time and date. A
lithium battery ensures that the clock continues to run when PiXtend or the Raspberry Pi
are switched off and not powered.
The Raspberry Pi (with Raspbian Linux as the operating system) automatically obtains the
current time from a server on the Internet in a network with Internet access. If, however, no
Internet connection is available ("island operation"), the Raspberry Pi and thus also the
operating system will forget the time after each shutdown. Here the RTC on PiXtend
comes into play.
The data exchange between Raspberry Pi and the RTC runs over the I²C bus.
Eigenschaft
Wert
Kommentar
Property
Value
Comment
Type of RTC
time and date
Seconds, minutes, hours, day of
month, month, day of week, year
and year; 12 and 24 hour format
Data connection
I²C bus
max. 100 kHz clock speed
Address 0x68 (104 decimal)
Table 28: Technical data - Real Time Clock
The battery used is not an accumulator that needs to be charged. The indicated buffer
time is reached without charging.
With regard to the UL / CSA approval of devices with PiXtend in the USA / Canada, the
solution on PiXtend is not critical. It could lead to problems if the battery charge circuit is
not designed according to the specifications of UL / CSA or the chip manufacturer.
Because the battery is not charged on PiXtend and is exclusively connected to the UL-
certified DS1307 (Maxim Integrated / Dallas Inc.) RTC chip, there is no problem with
acceptance.
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